Motion transmitting device



Aug. 11, 1959 J. J. LYNOTT 2,898,890

MOTION TRANSMITTING DEVICE Filed July 16, 1957 3 Sheets-Sheet 1 Fig 2 I 5 ROTATION 3607 INV TOR. JOHN J. LY/VOTT Aug. 11, 1959 J. J. LYNOTT 2,898,890

MOTION TRANSMITTING DEVICE Filed July 16. 1957 3 Sheets-Sheet 2 Q DISP ACEME/V ROTATION 360 DISPL A CEMEN T 0 fiOTAT/ON 360 Aug. 11, 1959 J. J. LYNOTT 2,898,890

MOTION TRANSMITTING DEVICE Filed July 16, 1957 3 SheetsSheet :s

MOTION TRANSMITTING DEVICE John J. Lynott, Los Gatos, Califi, assignor to International Business Machines Corporation, New York, N .Y., a corporation of New York Application July 16, 1957, Serial No. 672,269

Claims. (Cl. 121-41) States Patent O cylinder arrangement wherein substantially equal pressure is supplied to both sides of a piston, the piston being free to move both axially and rotationally within a cylinder. The cylinder is provided with an exhaust port. The lateral surface of the piston is wide enough to close off the exhaust port in the cylinder Whenever it is 10- cated thereover. Therefore, by the shaping of this lateral piston surface so that the exhaust port is exposed to one side of the piston by rotating it, an axial displacement or translation of the piston is produced due to the creation of a pressure difierential thereacross. This pressure difierential drives the piston in the direction of the exposed side of the port until the ditferential is cancelled by the arrival of the piston over the port.

In the sense that some mechanical cams convert rotational motion into a motion determined by the cams profile, this device can, by analogy, be described as a hydraulic cam since its longitudinal motion is determined by the elevation profile of the piston in the cylinder as it coacts with an exhaust port in the cylinder. It is an object of this invention, therefore, to provide a novel hydraulic device which produces a cam-like function.

In the prior art, so-called port sensing pistons, where in a piston has equal forces applied to its two end faces until a low pressure discharge port is opened on one side of the piston causing it to move in that direction, i.e. to seek or sense the low pressure port, normally employ conventional valves to control the discharge ports. According to the present invention, as the piston is rotated, it opens and closes the ports to be sensed. An other object of this invention is to provide a simplified hydraulic positioning device of the low pressure port sensing piston type, eliminating conventional valves.

In many positioning mechanisms it is desirable to convert an approximate or coarse input order into a precise output order, such as is required in the positioning of an object. This is usually done by employing a coarse drive together with a detenting means near the object. In such mechanisms, some small amount of slack is usually desirable at the coarse drive location. A feature of this invention is that it can be easily designed to provide such slack for accommodating remote mechanical detenting, as where a coarse and fine positioning is to be effected from two connected, but displaced, locations, respectively, the fine positioning requiring some freedom of movement at the coarse positioning location. It

,is, therefore, still another object of this invention to pro- .vide a coarse positioning device suitable for remote mechanical detenting.

associated with its instant rotational position.

Another form of the invention teaches that merely narrowing the port sealing surface to a thickness less than the diameter of the exhaust port provides selfdetenting so that the need for the usual additional detenting means described above is eliminated. Therefore,

it is another object of this invention to provide a selfdetenting positioning device.

A novel coarse-fine drive is produced by providing a plurality of controlled discharge ports to the above structure. Therefore, it is a further object of this invention to provide a novel hydraulic coarse-fine drive positioning mechanism of the port sensing type.

Closing the exhaust port with a controllable valve while the piston is being continuously rotated prevents the creation of any pressure differential across the piston and hence no axial displacement of the piston occurs while such valve is closed. However, opening the valve "will engage the piston by immediately providing the pressure differential to drive it to the axial position A valve controlling the exhaust port acts then as a clutch. It is, therefore, another object of this invention to provide a clutchable hydraulic cam.

It is another object of this invention to provide a positioning device capable of amplification of applied forces.

Other objects of the invention will be pointed out in the following description and claims and illustrated in the accompanying drawings which disclose, by way of example, the principle of the invention and the best mode which has been contemplated of applying that principle.

In the drawings: Fig. 1 is an isometric view of one form of the inven- "tion employing the piston of Fig. 2.

Fig. 2 is an isometric view of one embodiment of a piston of the invention.

Fig. 3 is a curve showing diagrammatically the general relationship between angular rotation and axial displacement for the piston of Fig. 2 when operated in the embodiment of Fig. 1.

Fig. 4 is an isometric view of another embodiment of the piston of this invention showing its relationship to port 12 (in invisible lines) when employed in the embodiment of Fig. 1.

port 12 (in invisible lines) when employed in the embodiment of Fig. 1.

Fig. 7 is a curve showing diagrammatically the general relationship between angular rotation and axial displacement for the piston of Fig. 6 when operated in the embodiment of Fig. 1.

Fig. 8 is an isometric view of another embodiment of the piston of this invention showing its relationship to port 12 (in invisible lines) when employed in the em bodiment of Fig. 1.

Fig. 9 is a curve showing diagrammatically the general relationship between rotation and displacement for the piston of Fig. 8 when operated in the embodiment of Fig. 1.

Fig. 10 is an isometric view of a coarse-fine drive embodying the invention using the piston of Fig. 8.

Referring to Figs. 1 and 2, the embodiment of the invention disclosed therein comprises a piston 20 and a cylinder 10 having inlet pressure ports 11, 11 in each end which lead to a common source of fluid under pressure such as an accumulator or reservoir (not shown) so that the pressure on both sides of piston 20 is the same- -'A to receive a bell-nut 14-and hose-15 for connection with the pressure source in the case of the ports 11,- lland a low pressure chamber or sump (not shown) in the case of port12.

asaaeeo r Inside cylinder-10 piston 201$ fixed to ashaft 1s xtending throuhg seals 17, 17 in each end of cylinder 10. Shaft 16 is free to revolve in either direction, as well as to move axially back and forthwithin cylinder 10.

Piston 20, fixed to shaft 16 for movement therewith, is comprised of two semicircular end pieces 18 and 18' spaced apart on shaft 16 and rotationally oriented 180 relative to each other. Pieces 18 and 18 are joined by a planar supporting member 19 which extends radially toward the inner surfaceof cylinder '10 and thus prevents fluid from flowing freely from one side of piston 20 to the other. However, some leakage will be present from side to side since it is preferred that piston 20 fit only loosely within cylinder 10. The outer cylindrical surfaces 21 and 21 of pieces 18 and 18' are as wide as port 12 and when positioned thereover will substantially close it off. However, by making surfaces 21 and 21 wider than port '12, some positive overlap may be provided in an amount equal to the difference between the width of the surfaces 21 or 21 and the diameter of port 12. As more fully explained below, this positive overlap provides some slack at the positioning device, if desired, to allow for mechanical detenting at a remote location.

In operation, shaft 16 is rotated, say clockwise as shown by arrow 23. Referring particularly to Fig. 1, this rotation causes the trailing edge 22 of surface 21 to un cover or expose port 12. This lowers the pressure to the left of the piston and thus provides a pressure differential which tends to drive iston 20 to the left. In this man ner, piston 20 willseek the exposed port 12 and be displaced to the left until surface 21' closes port 12. By closing port 12, the pressure differential is cancelled and shaft 16 and piston 20 come to rest at this location until port 12 is again uncovered substantially 180 later. Thus, continuous rotation of piston 20 produces a camlike back and forth translation thereof between two loca- .tions, the translation being determined by the elevation or stroke profile of piston 20. In other words, the trans latory output of the piston varies with the piston profile. The general relationship between translation of shaft 20 shown in Fig. 2 is illustrated diagrammatically in the graph of Fig. 3, wherein the horizontal coordinate represents rotation of shaft 16 from to 360 and the vertical coordinate represents axial displacement thereof.

Since the force required to rotate piston 20 is equal to the force of friction (F plus the force required to overcome inertia (F a collateral effect of creating a pressure differential across piston 20 is an amplification of the applied force in accordance with the formula ApA f'l' i) where Ap is the pressure differential across piston 20 and A is the effective area of one end of piston 20 acted upon by pressure differential Ap.

Although the invention has been generally described as a hydraulic device, it is to be understood that it can also be operated pneumatically.

Positive overlap of port 12 by surfaces 21 and 21' may be provided to allow piston 20 to move back and forth a small distance without uncovering port 12. Thus, by

merely widening surface 21 with respect to port 12, slack can be easily built into the system to accommodate remote mechanical detenting. In this condition, the invention provides an excellent coarse drive possessing the small freedom of movement thereat usually necessary for rernote mechanical detenting. Constructing surfaces 21 and 16 with respect to rotational movement thereof for piston 4 21' equal to or narrower than port 12, i.e. with no overlap or with negative overlap, surfaces 21 and 21' will center themselves right overport 12 and be self-detented, since the flow of fluid past each side of piston 20 through port 12 tends to equalize the pressure. Therefore, a coarse rotational positioning within limits of 180 effects a precise axial positioning of shaft 16 to one of two locations.

A further extremely useful and desirable feature of the hydraulic cam of this invention (unlike ordinary camfollower arrangements) is that it provides a clutchable" output motion by simply closing port 12 by any suitable valve, such as one of the solenoid actuated valves 101 shown in Fig. 10. In this condition, as shaft 16 is continuously rotated, no axial movement is produced, i.e. shaft 16 idles. Then by opening the valve, shaft 16 is positively positioned as explained above. In this manner shaft 16 is engaged and disengaged and a clutchable cam-like-motion is obtained.

The pistons of Figs. 4, 6 and 8 with their associated displacement curves, Figs. 5, 7 and 9, respectively, produced by varying the stroke profile of the piston, more fully illustrate the cam-like nature of the invention. Each of these pistons is designed for use in cooperation with cylinder 10 so that as they rotate they produce a'translatory motion dependent upon their profile, port 12 being .shown in invisiblelines in Figs. 4, 6 and 8 in order to indicate the association of pistons 40, 60 and there with.

The piston 40 of Fig. 4 has a toroidal piston portion 48 formed integrally upon an axis 16'. Portion 48 forms an angle (other than with shaft 16'. The outer port-sealing surface 41 of portion 48 is parallel with axis 16' and cylindrical so that piston 40 is free to rotate loosely within cylinder 10.

When piston 40 is used in cooperation with cylinder 10, itwill produce a constantly increasing axial displacement as it is rotated until it has been turned approximately At this point, it will reverse its axial direction and return in a constantly decreasing fashion, arriving at its original axial position when it has been rotated one complete revolution. The general relation between angular rotation and axial displacement for the piston of Fig. 4 is diagrammatically shown in the graph of Fig. 5.

Understanding that piston 40 will amplify a force applied to rotate shaft 16' in a manner similar to that described above regarding piston 20, and further understanding that shaft 16' is free to rotate in either direction, piston 40 is particularly useful as a control device such as in power steering applications.

Piston 40 best represents the invention, since any .a mount of rotational motion applied to it will result in a slight exposing .of port 12. This slight opening of port 12 with its attendant drop in pressure on the opened side of piston 40 will cause piston 40 to move axially in the direction of the lowered pressure [until the leading edge of surface 41 has passed over the exposed edge of port 12 and the port is again completely closed. Thus, the pistons elevation or stroke profile controls and determines the translation of its associated shaft just as by analogy the profile of a mechanical cam controls and determines the motion of an associated cam follower.

Another embodiment of the piston is shown in Fig. 6, including a piston 60 comprised of a shaft 16" having a helical piston portion 68 formed thereon. Portion 68 has a sufiiciently thick cylindrical sealing surface 61 to seal or interrupt port 12. In this regard, the term seal is to be understood as including conditions of positive and negative overlap, as well as a sealing surface 61 of exact port width. The beginning and ending of the helical portion 68 are joined by a planar connecting portion 69 in'order to prevent the free flow of fluid around piston 60.

When used in cooperation with cylinder 10, piston 60 provides a constantly increasing axial displacement as it is rotated, this general relationship being shown dia- 61a or 61b, of surface 61 is reached, the particular edge being dependent upon whether rotation is clockwise (61a) or counter-clockwise (61b).

In this manner, as port 12 is uncovered a small increment, the pressure on one side of piston 60 is reduced, thus'providing a pressure differential across the piston.

-This differential in pressure across piston 60 causes it to move axially in the direction of the lower pressure, i.e. toward the opened side of port 12. Piston 60 advances axially in this direction until surface 61 has been displaced enough to close off port 12, cancelling the diflerential. Assuming then, for example, a clockwise rotation of piston 60 (as viewed from the right in Fig. 6), piston 60 will be continuously opening port 12 to the right-hand side of piston 60, and just as soon as port 12 can be partially exposed, the resultant pressure differential will drive piston 60 to the right, thereby closing port 12. This continual exposing and closing of port 12 with resultant movement to the right continues until finally the edge 61a of surface 61 passes over port 12. This uncovers port 12 to the left-hand side of piston 60, causing a reversal of the direction of displacement and a resetting of shaft 16" to its original or starting position.

Another embodiment is shown in Fig. 8 including a piston 80 comprised of a shaft 16" having an enlarged central portion or collar 81 therearound. Completely encircling collar 81 from end to end and integral therewith is a stepped piston portion 88. Portion 88 could have been formed directly on shaft 16"; however, collar 81 is desirable to lend added rigidity and strength to portion 88. Portion 88 is comprised of a plurality of .connected steps, each step being somewhat axially offset a distance a, b, c or d dependent upon the desired axial displacement of shaft 16" to be associated with the particular step, i.e. a, b, c or d, respectively, (Fig.9). for purposes of clarity in explanation, the analogy of a stair step comprised of tread and riser portions will be followed to describe the operation of piston 80 when .used in cooperation with cylinder 10. Also, for purposes of simplicity the hidden side of piston 80 may be assumed to be the same as the side disclosed, although it will be obvious that limitless asymmetrical designs for portion 88 can be substituted. For example, a single step or a portion of an angular toroid or helix could be used to replace several of the steps of portion 88.

By rotating piston 80 clockwise as shown by arrow 82, the edge of tread a will uncover port 12 as it passes thereover. This will have the effect of lowering the pressure to the left of portion 88 causing piston 80 to be displaced to the left until riser w of portion 88 has sealed off port 12. Piston 80, therefore, has moved the length of tread a, shown diagrammatically in Fig. 9 as a. Throughout the angle of rotation while riser w is covering port 12 piston 80 dwells (shown as w in Fig. 9). When piston 80 has rotated sufliciently to cause riser w to pass from over port 12, the pressure drops again to the left of piston 80. By again lowering the pressure on the left side of piston 80, a pressure dilferential is created which drives piston 80 to the left the length of tread b, shown as b in Fig. 9. Piston 80 will stop itsleftward movement and dwell for x degrees of rotation (see Fig. 9) while riser x of portion 88 has covered port 12. In this stepwise fashion, piston 80 progresses to the left until riser z has been rotated past port 12. Since each successive uncovering of port 12 after riser z has passed port 12 and before riser v covers port 12, drops the pressure to the right of piston 80, the piston will follow a stepwise return to its original position.

Another form of this invention is the coarse-fine drive 'shown in Fig. 10, wherein a plurality of solenoid actuated valves 101, a flow divider arrangement 102 with associated ball check valves 103a, 103b, and a splined shaft 116 have been added to one of the piston embodiments, for example, piston of Fig. 8.

Referring now to Fig. 10, the coarse-fine drive comprises a cylinder having inlet pressure ports 111 in having a collar 109 thereon. Piston 104 is arranged to travel a short distance back and forth within a cylinder 105 so that at its extremes of travel it will shut off fluid flowing through outlet ports 106a and 106b in the ends of cylinder 105 leading to conduits 115a and 115b, respectively. Connecting cylinder 105 to a pressure source (not shown) is a pair of conduits 107, 107 for directing and dividing the flow of fluid to opposite sides of collar 109, as well as to opposite sides of piston 80 via conduits 115a and 115b.

Spring-loaded ball-check valves 103a and 10312 are arranged in conduits 115a and 115b, respectively, between cylinder 105 and ports 111 to prevent the flow of fluid Back to the pressure source. The purpose of flow divider 102 and valves 103 is to increase the speed with which piston 80 can be positioned between a plurality of discharge ports 112a, b and c as will be more 7 fully explained below.

Piston 80 is the same piston described above with reference to Fig. 8 and is connected to a shaft 116. The translatory motion of piston 80 is derived through shaft 116 which extends through seals 108, 108 at each end of cylinder 100 and is splined at one end to receive spline gear 110. Spline gear 110 provides rotational control of shaft 116 while permitting it freedom of axial movement.

Finally, discharge ports 112a, b and c are disposed between ports 111, 111. Ports 112 are maintained normally closed by valves 101 due to the urging of springs 113.

Associated with each valve 101 is a solenoid 114 for selective control thereof.

In operation, one of solenoids 114 is actuated, for example 114a, thereby opening its associated port 112a. By opening this port, the pressure drops to the left of piston 80. This drop in pressure is transmitted to the left side of piston 104 through valve 103a causing piston 104 to move to the left and close port 106a. This has the effect of directing the entire flow of fluid from the pressure source through port 106b, conduit 115b, valve 103b and in behind the right-hand side of piston 80. Piston 80 commences to move leftward due to the pressure differential thereacross and as it does, the fluid to its left is forced out port 112a to a low pressure sump (not shown). Valve 103a prevents this leftward piston movement from dislodging piston 104 from its position against port 106a. Consequently, the entire flow of fluid continues to be directed behind piston 80 until the appropriate riser of portion 88 covers port 112a, as explained above in regard to Fig. 8. In this manner a coarse positioning of shaft 116 is accomplished dependent upon which one of the plurality of valves 101 is opened. Pressure across piston 80 equalizes as soon as portion 88 closes off port 112a and this equalization of pressure is transmitted back to piston 104, thereby centering it in cylinder 105 so that it again divides the fluid flow. In lieu of the flow dividdescribed above with reference toFigJ 8. It is to be noted that this fine positioning can be done during the time piston 80 is traveling to its coarse location; thus considerable time may be saved in going from one finite location to another. Further, it is to be noted. that by providing portion 88 with negative overlap, valves 101 will be required to work against only a relatively low system pressure so long as valve 101 at the destination is open before valve 101 at the origin isclosed.

Further, the clutching feature described above also pertains to the embodiment of Fig. 10 by merely closing all valves 101 at the same time as shaft'116 continuously rotated.

Although the embodiment of the invention of Fig. 10 has been described in relation to the piston of Fig. 8, it is obvious that equally useful coarse-fine drives result from employing therein many other types of pistons such as those described above. I

While there have been shown and described and pointed out the fundamental novel features of the invention as applied to the preferred embodiment, it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art, without departing from the spirit of the invention. It is the intention, therefore, to be limited only as indicated by the scope of the following claims.

What is claimed is:

l. A motion transmitting device comprising a cylinder having a piston therein, and means for continuously supplying an uninterrupted inflow of pressure to each side of said piston, said piston being arranged so that when it is rotated the pressure is reduced on one side of the piston to cause the piston to be translated by pressure on the other side of the piston.

2. A motion transmitting device comprising a cylinder having a piston therein coacting with an exhaust port,

and means for supplying pressure continuously to each side of said piston, said piston being arranged so that when it is rotated the pressure is reduced on one side of the piston via opening said exhaust port to cause the piston 'to be translated by pressure on the other side of the piston.

3. A motion transmitting device comprising a cylinder closed at each end, a piston mounted for continuous rotation within said cylinder, an intakeport in each end of said cylinder for admitting fluid under pressure to each side of said piston, and an exhaust port in the wall of said cylinder coacting with said piston whereby rotation of the latter opens said exhaust port to reduce the pressure on one side of said piston thereby causing said piston to be translated in said cylinder by pressure from the other side of said piston.

4. A motion transmitting device comprising a cylinder closed at each end, a piston in said cylinder, an intake port in each end of said cylinder for continuously ad-' mitting fluid under pressure to each side of said piston, and an exhaust port in the wall of said cylinder coacting with said piston whereby a predetermined rotation of said piston results in a corresponding translation of said piston.

5. A motion transmitting device comprising a cylinder closed at each end, a piston in said cylinder, an intake port in each end of said cylinder for continuously admitting fluid under pressure to each side of said piston, and an exhaust port in the wall of said cylinder coacting with said piston, said piston being constructed such that a predetermined rotation thereof relative to said cylinder opens said exhaust port to reduce the pressure on one as a side of said piston thereby causing said piston to be translated in said cylinder correspondingly by pressure from the other side of said piston.

6. A motion transmitting device comprising a cylinder "closed at each end, a piston in said cylinder, anintake sport in each 'end of said cylinder for continuously ad- .niitting fluid under pressure to each side of said piston,

and an exhaust port in the wall of said cylinder coacting with said piston, said piston having an angular stroke profile for defining a predetermined relationship of rotation to displacement of said piston wherebyrotation of said piston opens said exhaust port to reduce the pressure on one side of said piston thereby causing said piston to be translated in said cylinder by pressure from the other side of said piston.

7. A motion transmitting device comprising a cylinder closed at each end, a piston mounted for continuous rotation within said cylinder, an intake port in each end of said cylinder for admitting fluid under pressure to each side of said piston, and an exhaust port in the wall of said cylinder coacting with said piston, said piston in the wall of said cylinder coacting with said piston, said piston having a stepped stroke profile for defining a predetermined relationship of rotation to displacement of 'said piston whereby rotation of said piston opens said exhaust port to reduce the pressure on one side of said piston thereby causing said piston to be translated in said cylinder by pressure from the other side of said piston.

9. A motion transmitting device comprising a cylinder closed at each end, a piston in said cylinder, an intake port in each end of said cylinder for admitting fluid under pressure continuously to each side of said piston, an exvhaust port in the wall of said cylinder coacting with said piston, and means for rotating said piston, whereby rotation of the latter opens siad exhaust port to reduce the pressure on one side of said piston thereby causing said piston to be translated in said cylinder by pressure from the other side of said piston.

10. A motion transmitting device comprising, in combination, a cylinder closed at each end, a piston in said cylinder, an intake port in each end of said cylinder for admitting fluid under pressure to each sideof said piston, a plurality of exhaust ports in the wall of said cylinder for coacting with said piston, said piston having a stroke profile which defines a predetermined relationship of rotation to displacement of said piston, means for selectively controlling each of said exhaust ports, and means for rotating said piston whereby actuating said control means opens one of said exhaust ports to effect a coarse positioning of said piston, and rotating said piston opens one of said exhaust ports to eficct a fine positioning of said piston.

References Cited in the file of this patent UNITED STATES PATENTS 2,244,296 Heinrich et al. June 3, 1941 

